Field of the Invention
This invention relates to the field of completion fluids for drilling applications, and more particularly to the field of reducing the friction between similar or dissimilar surfaces using an aqueous-based completion fluid disposed between the similar or dissimilar surfaces.
Background of the Invention
Drilling horizontally within an oil and gas reservoir can potentially produce a more productive well, because a horizontal well may allow for access to larger areas of an oil- and gas-bearing formation. As such, the longer the horizontal section of the well, the more productive the well may be. For this reason, it has become increasingly common to drill horizontally in many oil- and gas-bearing formations as well as utility and mining applications.
Increasing the length of the horizontal section of a borehole may be difficult when the length of the horizontal section surpasses the length of the vertical section. Further, the insertion of conduits, such as a drill pipe, may become increasingly difficult as the horizontal section is lengthened. For example, as the drill pipe is pushed further into the borehole, the amount of contact between it and other surfaces increases, and thus so would the amount of friction between the drill pipe and the other surfaces. Thus, the ability to push or rotate the drill pipe in the wellbore may become limited as the friction increases. Friction may also be present between a conduit and wellbore tools/wellbore materials inserted into the conduit. For example, wires or cables may be pushed or pulled into a conduit only so long as the amount of friction between the wires/cables and the conduit is low enough to allow for the wires/cables to be pushed or pulled. As discussed above, friction between two similar or dissimilar surfaces may increase faster in horizontal sections of a conduit relative to vertical sections of the conduit.
A specific example of the difficulty of drilling a horizontal section may be illustrated by the process of drilling bridge plugs from the casing. The drilling of bridge plugs is often performed with a fluid motor and bit on the end of a section of coiled tubing. An aqueous-based fluid may be pumped down the tubing, through the motor and bit, and back up the annulus inside the casing. The friction between a section of coiled tubing and the casing in the horizontal section of the borehole may become equal to the force available to move the coiled tubing along the horizontal section, at which point further drilling may not be possible.
As discussed, one method of reducing friction in oil, gas, and mining operations is to push a conduit with a mechanism that would drive the conduit into the borehole or well. This pushing may be accomplished by any mechanism that is capable of delivering a sufficient amount of force to the conduit such that the conduit is pushed into the borehole. This may be referred to as “snubbing the pipe.” In utility boring or mining operations, cables may be attached to the drill string to pull the conduits into or out of the borehole so as to overcome the friction between the conduit and the borehole. Further, in some horizontal drilling applications, rotating the conduit at a high enough RPM may reduce the amount of frictional contact between the conduit and any surfaces it contacts. This is commonly done during drilling and boring operations and may allow for longer horizontal sections to be drilled. However, not all conduits can be rotated. For example, when a jointed pipe is used, the pipe may be rotated along with the bit, and the friction resisting movement of the pipe along the borehole may be decreased. However, when coiled tubing is used, the coiled tubing cannot be rotated, and the friction resisting movement of the tubing along the borehole may be increased. Further, even when using jointed pipes, wells with directional changes resulting in “doglegs” or a crooked borehole, may restrict the amount of rotation that may be used. Moreover, when using these physical methods to reduce friction, friction may continue to build as the borehole is drilled, and the conduit is inserted deeper. Thus, eventually enough friction may be present to prevent further insertion or extraction of a conduit from the borehole. This effectively means that drilling rigs may sometimes drill longer horizontal sections than completion equipment can complete.
Friction reducers have proven effective in reducing the coefficient of friction between two metal substrates. Some examples may include the deposition of polymer particles onto a metal substrate. In these examples, the oil must have a charge association. However, this approach may be ineffective when there are not two metal substrates present to provide the deposition sites, or when fluid conditions, such as the fluid pH, change when in use, and these changed fluid conditions alter the charge association and prevent film buildup or transport of the friction reducers.
Consequently, there is a need for an organic nonhazardous biodegradable friction reducer that is not charge specific, does not require mechanical deposition to reduce the coefficient of friction, is usable between any type of media, and can function in any water condition regardless of the pH of the water or the presence of suspended or dissolved solids.